It is known to use a subsurface safety valve which is actuated to the open position by the application of hydraulic fluid from the well surface and which is moved to the closed position by biasing means such as an enclosed pressure gas chamber and a mechanical spring.
It is imperative that a safety valve must close under all circumstances and if there is a failure it must be failsafe in a closed position. As valves are set deeper in the well, pressurized chambers having compressed gas are used as a biasing force in addition to a biasing spring. U.S. Pat. Nos. 4,660,646 and 4,976,317 disclose gas biased safety valves which allow a valve to failsafe close if the gas charge is lost.
The prior failsafe gas safety valves included numerous parts and seals. The present invention is directed to a minimum number of parts and seals and this reduction will reduce manufacturing cost, decrease friction, reduce assembly time, and improve reliability. In addition, the present improved safety valve will overcome other problems associated with prior art valves.